Coil structure for producing a magnetic field in an electric circuit interrupter



Nov. 24, 1964 J. w. PORT 3,158,722 COIL. STRUCTURE F PRODUCIN MAGNETI IELD IN AN ELEC 1 cm T INTERRUPTE Filed Nov. 1962 INVENTORJ JOSEPH W. PORTER,

ATTORNEY.

United States Patent COHL STRUCTURE FGR PRODUCING A MAG- NETIC IFKELD IN AN ELECTRIC CIRCUIT INTERRUPTER Joseph William Porter, Media, Pa, assignor to General Electric Company, a corporation of New York Filed Nov. 14, 1962, Ser. No. 237,532 11 Claims. (Cl. 200-147) This invention relates to coil structure that can be electrically energized to produce a magnetic field. The invention is particularly, though not exclusively, concerned with coil structure of this character that is used for producing a magnetic field in a vacuum-type circuit interrupter.

Certain vacuum-type circuit interru'pters have been proposed in which a coil is connected in series with the contacts of the interrupter. The purpose of this coil has been to produce a magnetic field that aids the interrupter in extinguishing the usual are that is drawn during an opening operation.

The use of such coils has presented a number of problems. One of these problems has been a matter of mechanical strength. Since the coil is in series with the contacts, it will be traversed by the high currents that flow through the contacts during abnormal overcurrent and fault conditions. These high currents produce magnetic forces on the turns of the coil that increase as the square of the current. To resist these high magnetic forces, special reinforcing means must be incorporated into the coil, and this tends to complicate the coil and make it more massive and expensive. This mechanical strength problem is further aggravated by the requirement that the vacuum interrupter must be baked at high temperatures for prolonged periods to produce the necessary degassing of the pants. This bakeout tends to weaken conventional coil structures.

Another problem has resulted from the fact that previously proposed coils capable of carrying the high currents involved have been quite massive and have consumed a large amount of volume. This has made it difficult to include the coil in the small evacuated envelope of the interrupter since space is usually at a premium in the envelope.

An object of my invention is to provide coil structure that consumes an exceptionally small amount of volume beyond that otherwise needed by the interrupter, adds little to the mass of the interrupter parts, and has a high mechanical strength.

In carrying out my invention in one form, I provide an electric circuit interrupter that comprises a pair of electrodes between which an arc is adapted to be established. One of the electrodes is supported on an elongated rod of highly conductive material that is electrically connected at its inner end to the electrode. Current-directing means is provided for forcing current flowing through the rod to said one electrode to follow a generally helical path in the region of the rod adjacent said one electrode. This current directing means comprises a plurality of slots extending transversely of the rod at locations closely spaced-apart longitudinally of the rod in the region adjacent said one electrode. Each of these slots extends only partially through the rod to leave a portion of the rod intact in a region longitudinally aligned with the slots. The intact portions at consecutive locations along the length of the rod are angularly spaced in the same angular direction from the immediately preceding intact portions, thus defining a highly conductive path that extends progressively around the rod as it traverses the rod longitudinally. In a preferred form of the invention, inserts of a low conductivity material are fitted Within the slots. For a better understanding of the invention, reference "ice may be had to the following description taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view through a vacuum type circuit interrupter embodying one form of the invention.

FIG. 2 is constituted by a series of cross-sectional views taken along the lines aa, b-b, cc, and dd of FIG. 1.

FIG. 3 is a cross-sectional view taken along the line 3-3 of FIG. 4-.

FIG. 4 is an enlarged elevational view of a portion of the structure shown in FIG. 1.

FIG. 5 shows a modified form of the invention.

Referring now to FIG. 1, there is shown a vacuumtype circuit interrupter comprising a highly evacuated envelope 11. This envelope 11 comprises a tubular housing 12 of glass or other suitable insulating material and a pair of end caps 13 and 14 disposed at opposite ends of the tubular housing 12 and joined to the tubular housing by suitable vacuum-tight seals 15. A conventional shield 16 of tubular form protects the insulating walls of the tubular housing 12 from being impaired by metallic vapors condensing thereon.

Disposed within the evacuated envelope 11 are a pair of relatively movable contacts or electrodes 17 and 18 of a disk configuration. The upper contact 17 is a stationary contact that is supported from the upper end cap 13 by means of an elongated rod Ztl of a highly conductive material such as copper. The rod 20 is joined at its upper end to the upper end cap 13 and at its lower end to the disk contact 17, preferably by brazing.

The lower contact 18 is a movable contact that is supported on the upper end of a longitudinally-movable contact-operating rod 22. This contact-operating rod 22 is also formed of a highly conductive material such as copper. The contact-operating rod 22 extends through an opening in the lower end cap M, and a flexible metallic bellows 24 provides a seal about the rod 22; to allow for vertical movement of the rod without impairing the vacuum inside the envelope ll. As is shown in FIG. 1, the bellows is joined in sealed relationship to the end cap 14 and operating rod 22 at its respective opposite ends.

The interrupter of FIG. 1 is shown in an open position with the contacts 17 and i8 separated. Closing of the interrupter is etiected by driving the movable contact l3 upwardly into engagement with the stationary contact 17. Opening is elitected by returning the movable contact 18 from its position of engagement (not shown) to the position shown in FIG. 1. When the movable contact i8 is driven downwardly during an opening operation, an are, such as shown at St), is established between the contacts 17 and 13. To aid in extinguishing this are 3%, I provide behind the contacts 17 an electromagnet in the form of coil structure 34 that when electrically energized creates a radial magnetic field 36 in the gap between the two contacts. This radial magnetic field acts in a known manner to drive the arc in a circumferential direction about dish contacts 17 and 18, thereby reducing are erosion and facilitating circuit interruption.

Preferably, an additional coil structure or electromagnet 38 is provided behind movable contact 18 to create an additional radial magnetic field 40 that supple ments the magnetic field 3-6. As will soon appear more clearly, like poles of the two electromagnets 34 and 38 face each other so that the two magnetic fields supplement rather than cancel each other in the gap region. To prevent eddy currents from being induced in the contacts 17 and 18 to such an extent as would materially cancel the magnetic fields as and id, each of these contacts l7 and 15; is provided with a radially-extending slot (not shown).

Previously-proposed electromagnets for this application have generally been made of a conductor spirally wound into a coil and connected in series with the contacts. An example of such a coil is shown in US. Patent 2,027,836Ranl;in et al., assigned to the assignee of the present invention. Since the current flowing through an interrupter can reach very high values and since this current must traverse the series-connected coil, the conductors that have been used in prior coils have necessarily been quite heavy. This has resulted in a massive coil structure that has consumed an undue amount of space inside the envelope. it has also been necessary to provide these prior coils with special reinforcements to enable them to withstand the high magnetic force present. Such reinforcements disadvantageously add to the expense and size of the coil.

1 have provided a coil structure for each of the electromagnets and 33 that largely overcomes the aforementioned problems. This coil structure comprises a series of transversely extending slots provided in each rod at the inner end of the rod adjacent the contact structure mounted thereon. FIG. 2 illustrates the configuration of these slots, as they appear in a series of cross sections taken along transverse planes rz-n, bb, cc, and d-d of FIG. 1. It will be noted from FIG. 2 that each transverse slot 5t extends only partially through the rod 20 and thus leaves a portion of the rod intact at the inner end or" the slot in a region longitudinally aligned with the slot. These intact portions are designated 52 in the illustrations that constitue MG. 2. Proceeding downwardly through the consecutive locations b-b, c-c, and drt', it will be noted that the intact portions 52 are angularly displaced in the same angular direction from the intact portion at the immediately preceding location. Thus, the current path through the coil 34 extends progressively about the rod in a circumferential direction as it traverses the length of the rod, thus following a generally helical path. In sections aa through d-d of FIG. 2 the current path is progressively shifted counterclockwise through approximately 360 degrees of the rod periphery, thus acting as approximately one turn of the coil.

It is to be understood that rod 2% is substantially completely intact in transversely extending planes located intermediate the planes depicted in FIG. 2. Through these completely intact circular sections, current will flow generally circumferentially of the rod between the angularly-displaced portions 52 at axially opposed sides of the intact circular section. For example, referring to PEG. 3, there is an intact circular section between the two portions 52 shown at the bottom and righ hand side of rod Zil. Through this circular section current will ilow circumferentially of the rod between these angularly-displaced intact portions 52. The current tends, however, to con-- centrate in the region of the rod which is located closest to the two intact portions 52, as is indicated by the dotted lines 53 of FIG. 3, thus preserving the predominantly circumferential direction of the current path.

To preserve the mechanical strength of the rod 2%) despite the presence of the slots fill, an insert as f form having the same cross-section as the slot is disposed within each slot. These inserts as are formed of a low conductivity material such as stainless steel each is brazed on its opposite faces to the wall of the slot. This is best shown in the enlarged view of FIG. 4, where the insert is shown brazed along its -aces 62 to the adjacent walls of the slot. The presence of the inserts so helps to prevent the slots from collapsing in response to extreme com" re ive forces on the roll, and the brazing at 52- helps to prevent the slots from opening up in response to any high tensile forces that might be applied to the rod.

It will be apparent that the coil structure 3 adds little or nothing to the volume or the mass of the parts otherwise present in the circuit interrupted. in this re gard, note that the inserts dtl are generally confined to a A. space bounded by the outer periphery of the rod 20 and are not appreciably more massive that the sections of the original rod that had been moved to accommodate the inserts.

The lower coil structure 33 is formed in essentially the same manner as the upper coil structure 34- except that it is eflectively wound in an opposite direction to the upper coil structure, i.e., clockwise as the current lows downwardly through the coil structure This opposite winding of the two electromagnets results in like poles of the two magnets facing each other and the field acting to supplement each other, as shown, in the space between the two contacts.

Although my coil structure is particularly adapted for use in vacuum type circuit interrupters, as illustrated, it should be understood that it can also be used to advantage in other applications where it is desired to provide a compact, mechanically strong coil structure for producing a magnetic field.

it should be further understood that the cross-sectional shape of the rod and of the inserts can be varied without departing from my invention in its broader aspects. For example, the rod 2% may be of a rectangular cross-section as shown in FIG. 5, with the intact portions 52 being located at a corner of the rod and the remainder of the rod cross-section being consumed by the transversely extending slot Stl with the insert 60 fitted therein. FIG. 5 corresponds to section d--d of FIG. 2. At consecutive locations along the length of the rod of FIG. 5, the intact portion 52 would appear at different corners progressively shifted about the periphery of the rod, in a manner similar to that illustrated in FIG. 2.

While I have shown and described particular embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from the invention in its broader I aspects. I therefore intend in the appended claims to cover all such changes and modifications as fall Within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1.In an electric circuit interrupter that comprises a pair of electrodes between which an arc is adapted to be established,

(a) an elongated rod of highly conductive material for supporting one of said electrodes,

(12) means for electrically connecting said one electrode to said rod at the inner end of the rod,

(c) current-directing means for forcing current flowing through said rod to or from said one electrode to follow a generally helical path in the region of said rod adj aoent said one electrode,

(d) said current-directing means comprising a plurality of slots extending transversely of said rod at locations closely spaced-apart longitudinally of said rod in the region adjacent said one electrode,

(2) each of said slots extending only partially through said rod to leave a portion of said rod intact in a region of said rod longitudinally aligned with said slot.

2.'The structure of claim 1 in which said intact portions at consecutive locations along the length of said rod are angularly displaced in the same angular direction from the intact portion at immediately proceeding locations so as to define a hi hly conductive path that extends progressively about said rod as it traverses said rod longitudinally.

3. The structure of claim 2 in combination with inserts of a low conductivity material fitted Within said slots.

4-. The structure of claim 1 in combination with inserts of a low conductivity material fitted within said slots.

5. The structure of claim 1 in which there are substantially intact sections of said rod disposed intermediate the locations of adjacent slots.

6. In an electric circuit interrupter of the type that comprises a pair of relatively movable electrodes between (15) current directing means for forcing current flovvwhich an arc is adapted to be established, ing between longitudinallyepaced points on said rod (a) a pair of elongated rods of a highly conductive to follow a generally helical path in a predetermined material for respectively supporting said electrodes, region of said rod,

([1) means for electrically connecting each of said elec- 5 (c) said current-directing means comprising a plurality trodes to its respective rod at the inner end of the of slots extending transversely of said rod at locarod, tions closely spaced-apart longitudinally of said rod (c) current-directing means in each rod for forcing in said predetermined region,

current flowing through said rod to or from its re- (d) each of said slots extending only partially through spective electrode to follow a generally helical path 19 said rod to leave a portion of said rod intact in a in the region of said rod adjacent its respective elecregion longitudinally aligned with said slot. trode, 9. The structure of c aim 8 which the intact portions (d) the current-directing means in each rod comprisat consecutive locations along the length of said rod are ing a plurality of slots extending transversely of said angularly displaced in the same angular direction from rod at locations closely spaced-apart longitudinally 15 the intact portions at immediately preceding locations of said rod in the region adjacent the electrode of so as to define a highly conductive path that extends prosaid rod, gressively about said rod as it traverses the rod longitudi- (e) each of said slots extending only partially through nally.

said rod to leave a portion of said rod intact in a 10. The structure of claim 8 in combination with inregion longitudinally aligned With said slots. 20 serts of a low conductivity niaterialfitted Within said slots.

7. The circuit interrupter of claim 6 in combination 11. The structure of claim 8 in which there are sub- With inserts of a low conductivity material fitted within stantially intact sections of rod disposed intermedisaid slots. ate the locations of adjacent slots.

8. Means for creating a magnetic field comprising: (a) a rod of a highly conductive material, 25 No references cited. 

1. IN AN ELECTRIC CIRCUIT INTERRUPTER THAT COMPRISES A PAIR OF ELECTRODES BETWEEN WHICH AN ARC IS ADAPTED TO BE ESTABLISHED, (A) AN ELONGATED ROD OF HIGHLY CONDUCTIVE MATERIAL FOR SUPPORTING ONE OF SAID ELECTRODES, (B) MEANS FOR ELECTRICALLY CONNECTING SAID ONE ELECTRODE TO SAID ROD AT THE INNER END OF THE ROD, (C) CURRENT-DIRECTING MEANS FOR FORCING CURRENT FLOWING THROUGH SAID ROD TO OR FROM SAID ONE ELECTRODE TO FOLLOW A GENERALLY HELICAL PATH IN THE REGION OF SAID ROD ADJACENT SAID ONE ELECTRODE, (D) SAID CURRENT-DIRECTING MEANS COMPRISING A PLURALITY OF SLOTS EXTENDING TRANSVERSELY OF SAID ROD AT LOCATIONS CLOSELY SPACED-APART LONGITUDINALLY OF SAID ROD IN THE REGION ADJACENT SAID ONE ELECTRODE, 